A noncontact coupler using magnetic coupling technique is used as a means of supplying power to or charging an electric car, electric bicycle or other electric apparatuses.
FIGS. 16A–16D illustrate a structure of a prior art noncontact coupler. In this figure, FIG. 16A is a perspective view of a magnetic core 1′, FIG. 16B is a plan view of FIG. 16A; FIG. 16C is a cross-sectional view of a noncontact coupler using the core 1′; and FIG. 16D is an equivalent circuit of the same.
As shown in the figures, the noncontact coupler includes a pair of magnetic cores 1′, 1′, each of which forming a U-shaped open magnetic path, and a primary coil L1 and a secondary coil L2 separately wound around the respective cores. The cores 1′, 1′ are opposed to each other with both open magnetic face sides of the respective cores 1′, 1′ in proximity to form an annular closed magnetic path B to allow the primary coil and the secondary coil to transmit AC power (high frequency power) to each other.
In this case, the core 1′ in which the primary coil L1 is wound corresponds to a primary of a transformer and the core 1′ in which the secondary coil L2 is wound corresponds to a secondary of a transformer respectively. The primary and the secondary are closely located each other at the interval of d and work as though it constituted one transformer.
The magnetic core 1′, 1′ is made of for example a ferrite magnetic body and integrally formed in a disc-shape. At one side of said disc magnetic core 1′, a circular groove 52 is formed so that the coil L1, L2 is wound (received) therein, and the U-shaped open magnetic path is formed as detouring around the circular groove 52. Inside the annular groove 52, namely in the center of the disc, is formed a medium leg 51 which forms one pole face of the U-shaped open magnetic path. On the other hand, an outer circumference of the annular groove 52, namely outside of the disc, is formed an annular outer leg 53 and the other pole face of the U-shaped open magnetic path.
In the above noncontact transmission coupler, it is necessary to strengthen the magnetic coupling between the primary coil and the secondary coil for improving efficiency of power transmission. In other words, it is necessary to keep the magnetic coupling coefficient between the primary/secondary as high as possible. Then, in the prior art, a magnetic coupling was maximized between the cores 1′, 1′ by means of enlarging the area of the pole face (pole area) as large as possible. Because the wider the area of magnetic surface facing to each other is made, the tighter the magnetic coupling becomes. Therefore, the cores 1′, 1′ are formed in a solid integral structure, namely filled structure, having no void as a whole and to have a large magnetic pole area as large as possible. See Japanese Patent Application Laid-open Publication No. 2000-150273.
In the noncontact coupler, there were some problems as to its characteristics and structure stated below.
Namely, the structure confining the magnetic path B into the magnetic cores 1′, 1′ each having a filled integral structure can get high coefficient of the magnet coupling when both the magnetic cores 1′, 1′ are faced to each other concentrically. However, as shown in FIGS. 17A, 17B, when a lateral displacement (side displacement) arises between both the magnetic cores 1′, 1′, then the coupling coefficient fairly decrease by the lateral displacement h. Convenience in handling of the noncontact coupler will be deteriorated when the changing rate of the coupling coefficient for the displacement is large, because positioning between the primary and secondary requires accuracy.
Further, most weight of the noncontact coupler owes the magnetic cores (1′, 1′) of solid integral structure, increase in weight was unavoidable and this interrupted attempt to lighten the noncontact coupler.
The first object of the present invention is to improve usability of the noncontact coupler while securing its performance.
The second object of the present invention is to improve usability of the noncontact coupler by means of lightening the weight while securing its performance.
The third object of the present invention is to improve usability of the noncontact coupler by broadening tolerance in positioning of the primary and secondary cores.
Other objects and features according to the invention described above would be made clear by the following description of the specification and drawings.